The exhaust heat exchanger according to German Patent No. DE A 199 07 163 includes a housing in which a tube bundle is located, the tube ends being welded in two tube plates that are in turn welded to the housing. The exhaust flows through the tubes and the tubes are cooled on the outside by coolant drawn from the coolant cycle of an internal combustion engine. During operation of this kind of exhaust heat exchanger, damage, particularly breaks or cracks to the tube plate or to the welded tube plate joints, may occur, due to the very high alternating temperature stresses on the exhaust side. The tube plate of the known exhaust heat exchanger has a wall thickness on the order of 1 mm. Roughly rectangular openings are provided in this relatively thin tube plate, and they have a rather small separation, i.e., a relatively narrow web between neighboring openings. The web width is chosen to be relatively small in order to achieve a compact tube arrangement for the exhaust heat exchanger. For manufacturing reasons, however, the web width cannot be significantly less than the wall thickness of the plate. As a result, the web width, and thus, the spacing between the tubes, must increase to maintain manufacturability when tube plates with increased wall thicknesses are used. However, a larger web width reduces the efficiency of the exhaust heat exchanger and increases the spacing between the tubes, thus reducing their mutual support.
The present invention provides a tube plate for an exhaust gas heat exchanger that overcomes the limitations of known devices, as described above. These and other advantages of the present invention, as well as other inventive features, will be apparent from the description of the invention provided herein.